1. Field of Invention
This invention relates to the long term stabilization of enzymes contained in liquid laundry detergent compositions.
2. Prior Art
The desirability of using enzymes in cleaning compositions is well known. For example, lipase enzymes are useful in their ability to reduce macro molecules such as fat into components that can be easily washed away with detergents and/or water. Protease enzymes, for example, are useful for their ability to reduce proteinaceous stains which can then also be readily washed away.
The stability of enzymes in current heavy duty liquid laundry detergent compositions (HDLs) is generally poor. The surfactants found in the detergent compositions can induce denaturation of the enzyme and, when a protease is present, the protease will cause proteolytic digestion of the other enzymes (if not a protease) or of itself in a process called autolyses.
Proteins taught in U.S. Pat. No. 4,842,767, such as casein, are known to improve enzyme stability in HDLs. Other approaches used for stabilization of enzymes in HDLs include the use of low molecular weight carboxylic acids (preferably formate) and calcium such as disclosed in U.S. Pat. Nos. 4,305,837, 4,318,818, and 4,490,285; and the use of boron containing compounds in combination with a short chain carboxylic acid and calcium as shown in U.S. Pat. No. 4,537,707. U.S. Pat. No. 4,842,758 teaches an enzyme stabilizing system of a boron compound, a protein such as casein and a C.sub.3 -C.sub.8 organic alpha-hydroxy carboxylic or polycarboxylic acid.